The present exemplary embodiments relate to the imaging arts, and find particular application in conjunction with low and high-density cell detection, locating, and identifying in blood smears, biological assays, and the like across distinct imaging systems, and will be described with particular reference thereto. However, it is to be appreciated the exemplary embodiments will also find application in imaging, locating and identifying other types of low- or high-density features on various substantially planar surfaces and samples, such as imaging semiconductor wafers, imaging particulate contaminants in fluids or thin solid films, and so forth, with such imaging finding specific uses in the printing arts, electronic arts, medical arts, and other scientific and engineering areas.
In rare cell studies, a particular problem arises due to the typically low concentration of the rare cells in the blood or other body fluid. In a typical rare cell study, blood is processed to remove cells that that are not needed. Then a fluorescent material is applied that attaches to antibodies, which in turn selectively attach to a cell surface or cellular protein of the rare cells. The cellular proteins may be membrane proteins or proteins within a cell, such as cytoplasm proteins. The antibodies may also attach to other types of molecules of the rare cell, as well as to DNA.
The fluorescent material may be a fluorescent marker dye or any other suitable material which will identify the cells of interest. A smear treated in this manner, which may include the blood and/or components of the blood, is prepared and optically analyzed to identify rare cells of the targeted type. For statistical accuracy it is important to obtain as large a number of cells as required for a particular process, in some studies at least ten rare cells should be identified, requiring a sampling of at least ten million cells, for a one-in-one-million rare cell concentration. Such a blood smear typically occupies an area of about 100 cm2. It is to be understood, however, that this is simply one example and other numbers of cells may be required for statistical accuracy for a particular test or study. Other cell identifiers which are being used and investigated are quantum dots and nano-particle probes. Also, while a rare cell is mentioned as a one-in-one-million cell concentration, this is not intended to be limiting and is only given as an example of the rarity of the cells being sought. The concepts discussed herein are to be understood to be useful in higher or lower levels of cell concentration.
In this regard, the ability to scan large numbers of cells at a high rate is considered a key aspect which increases the throughput of testing processes. Therefore, it is considered valuable to provide a system which improves the speed, reliability and processing costs which may be achieved by cell detection systems and/or processes.
One particular cell detection technique is known as fluorescence in situ hybridization (FISH). This process uses fluorescent molecules to paint genes or chromosomes. The technique is particularly useful for gene mapping and for identifying chromosomal abnormalities. In the FISH process, short sequences of single-stranded DNA, called probes, are prepared and which are complementary to the DNA sequences which are to be painted and examined. These probes hybridize, or bind, to a complementary DNA, and as they are labeled with a fluorescent tag, it permits a researcher to identify the location of sequences of the DNA. The FISH technique may be performed on non-dividing cells.
Another process of cell detection is flow cytometry (FC), which is a means of measuring certain physical and chemical characteristics of cells or particles as they travel in suspension past a sensing point. Ideally the cells travel past the sensing point one by one. However, significant obstacles exist to achieving this ideal performance, and in practice a statistically relevant number of cells are not detected due to the cells bunching or clumping together, making it not possible to identify each cell individually. In operation a light source emits light to collection optics, and electronics with a computer translates signals to data. Many flow cytometers have the ability to sort, or physically separate particles of interest, from a sample.
Another cytometry process is known as laser scanning cytometry (LSC). In this system, data is collected by rastering a laser beam within the limited field of view (FOV) of a microscope. With laser rastering, the excitation is intense and for single or multiple wavelengths, filtering permits a differentiation between dyes responsive at distinct wavelengths. This method provides equivalent data of a flow cytometer, but is a slide based system. It permits light scatter and fluorescence, but also records the position of each measurement. By this design, cells of interest can be relocated, visualized, restained, remeasured and photographed.
While the above-noted systems are directed to creating faster scan rates, they nevertheless still have relatively small fields of view (FOV), such as microscopes. This will, therefore, still result in speeds which do not reach the desired scan rates.
In view of this, the previously noted and incorporated U.S. application Ser. Nos. 10/271,347 and 10/616,366 disclosed a fiber array scanning technology (FAST) that increases the speed at which scanning of a sample and the detection of potential or candidate rare cells may be accomplished, lending itself to the investigation of large samples.
These applications addressed the issue that while use of the described FAST scan system provides significant benefits in the detection of potential or candidate rare cells, the resolution obtainable by the FAST system may not be sufficient for certain studies. U.S. Ser. No. 10/616,366 addressed this issue by describing a system where a sample—is provided following scanning in the FAST scan system—to a device having a higher resolution than may be obtained by the described FAST scan system permitting an increased level of investigation. A particular type of high resolution device is a fluorescent microscope, or any other imaging system such as previously described herein or otherwise known. The high resolution device is described as either being integrated with the FAST scan system, or once the FAST scan process has been completed, the sample (or a data file containing an image of the sample) is transferred to a separate high-resolution device for more specific identification of rare cells.
A particular concern with undertaking this additional investigation, is acquiring location information of the designated candidate rare cells when the sample is transferred from the FAST scan system to the high resolution system. Since, as mentioned the number of cells being scanned in an investigation may be from one million to 50 million or more, where the rare cells may be at a very low concentration. Therefore, when these candidate rare cells—identified in the FAST scan system—are transferred to a microscope system, locating these one-in-a-million cells, even when previously identified, is a time-consuming and at times nearly impossible task.
In order to improve the investigation process, it is important to be able to designate the locations of the detected candidate rare cells in the FAST scan system and to determine corresponding location information for use in a high resolution investigation.
Presently, this is accomplished by a user attempting to visually identify an area on a sample where the candidate rare cells have been detected. However, this is a time-consuming, inaccurate process, and does not lend itself to high-speed review and investigations.
Issues related to the transfer of candidate rare cells from the FAST scan system to a higher resolution system is that the higher resolution system has a small field of view (FOV), and that the two systems have distinct positional coordinate spaces. Therefore, even when locations of the candidate rare cells are identified in the FAST scan system coordinate space, this information is not usable when the candidate rare cells are transferred to the higher resolution system. Likewise, when coordinate locations are observed in the higher resolution system, it is sometimes desirable to backward locate those positions into the original FAST scan coordinate system.